This invention relates to an improvement of a vacuum switch which is provided with a function of a disconnecting switch.
It is well known that a vacuum switch can interrupt a large current by separating contacts from each other by a small distance and that the surfaces of the contacts are roughened by electric arc generated at the time of interrupting the large current which results in the lowering of the insulating strength. It is found that the shorter the distance between the contacts is, the higher the current interrupting capability becomes, and in view of this fact, there has been proposed two-stage operation wherein the contacts are firstly separated by a distance sufficint for withstanding the recovering voltage after the current interruption and then separated by a large distance to withstand against a predetermined maximum voltage, for example, impulse voltage.
Generally, in an electric power system, a circuit interrupter is used in combination with a disconnecting switch.
From the foregoings it has been proposed an improved vacuum switch incorporating the functions of a current interrupter and a disconnecting switch and having a high interrupting capability and high insulating strength by separating the arc extinguishing chamber of the vacuum switch into two parts, one for current interruption and the other for insulation, thus acting as a disconnecting switch.
Furthermore, in a conventional vacuum switch, an operator cannot observe the inside of the vessel and particularly, the fact that whether the contacts are in opened or closed state for maintenance or inspection of the switch.